You could add a counter, at the start of the automation set it to 90, Then add a loop into the automation that delays for 1 minute and decrements the counter. When the counter hits zero, exit the loop and turn the extractor off.
The second approach is create a template that calculates the number of remaining minutes. To do this first create an input_date helper and populate it with the time it should turn off. Second create a template the calculates the time remaining between the helper and now(). Third when this template goes to below 1 run the automation to turn the extractor off.
The first approach is simpler based on what you have already. The second approach improves flexibility as it can deal with situations like the extractor gets turned off manually then turned back on.